Coronary Doppler intensity changes during handgrip: a new method to detect coronary vasomotor tone in coronary artery disease

Practical guidance for the implementation of stress echocardiography

Exercise stress testing has been widely undertaken for the diagnosis of heart diseases. The accurate assessment of clinical conditions can be conducted by comparing the findings obtained from the results of stress echocardiography with the changes in the blood/heart rate and electrocardiograms. Numerous overseas studies have reported the utility of stress echocardiography in diagnosing myocardial ischemia; in Japan, the use of this modality for this purpose was included in the national health insurance reimbursable list in 2012. Nevertheless, stress echocardiography is far from being a widespread practice in Japan. This might be due to insufficient equipment (e.g., ergometers, space for test implementation) at each medical institution, shortage of technicians and sonographers who are well experienced and who are responsible for obtaining images during stress testing. The other possible reasons include the limited evidence available in Japan and the lack of a standardized testing protocol. Further dissemination of the practice of exercise stress echocardiography in this country is deemed necessary to establish satisfactory evidence for the use of stress echocardiography in the Japanese population. To this end, efforts are underway to develop a standardized protocol and report format to be adopted throughout Japan. We here present a guideline created by the Guideline Development Committee of the Japanese Society of Echocardiography that describes safe and effective stress echocardiography protocols and report formats. The readers are encouraged to perform exercise stress echocardiography using the proposed template for consensus document and report attached to this guideline.

Coronary responses to cold air inhalation following afferent and efferent blockade

Cardiac ischemia and angina pectoris are commonly experienced during exertion in a cold environment. In the current study we tested the hypotheses that oropharyngeal afferent blockade (i.e., local anesthesia of the upper airway with lidocaine) as well as systemic β-adrenergic receptor blockade (i.e., intravenous propranolol) would improve the balance between myocardial oxygen supply and demand in response to the combined stimulus of cold air inhalation (-15 to -30°C) and isometric handgrip exercise (Cold + Grip). Young healthy subjects underwent Cold + Grip following lidocaine, propranolol, and control (no drug). Heart rate, blood pressure, and coronary blood flow velocity (CBV, from Doppler echocardiography) were continuously measured. Rate-pressure product (RPP) was calculated, and changes from baseline were compared between treatments. The change in RPP at the end of Cold + Grip was not different between lidocaine (2,441 ± 376) and control conditions (3,159 ± 626); CBV responses were also not different between treatments. With propranolol, heart rate (8 ± 1 vs. 14 ± 3 beats/min) and RPP responses to Cold + Grip were significantly attenuated. However, at peak exercise propranolol also resulted in a smaller ΔCBV (1.4 ± 0.8 vs. 5.3 ± 1.4 cm/s, P = 0.035), such that the relationship between coronary flow and cardiac metabolism was impaired under propranolol (0.43 ± 0.37 vs. 2.1 ± 0.63 arbitrary units). These data suggest that cold air breathing and isometric exercise significantly influence efferent control of coronary blood flow. Additionally, β-adrenergic vasodilation may play a significant role in coronary regulation during exercise.

Coronary blood flow responses to physiological stress in humans

Animal reports suggest that reflex activation of cardiac sympathetic nerves can evoke coronary vasoconstriction. Conversely, physiological stress may induce coronary vasodilation to meet an increased metabolic demand. Whether the sympathetic nervous system can modulate coronary vasomotor tone in response to stress in humans is unclear. Coronary blood velocity (CBV), an index of coronary blood flow, can be measured in humans by noninvasive duplex ultrasound. We studied 11 healthy volunteers and measured beat-by-beat changes in CBV, blood pressure, and heart rate during 1) static handgrip for 20 s at 10% and 70% of maximal voluntary contraction; 2) lower body negative pressure at -10 and -30 mmHg for 3 min each; 3) cold pressor test for 90 s; and 4) hypoxia (10% O(2)), hyperoxia (100% O(2)), and hypercapnia (5% CO(2)) for 5 min each. At the higher level of handgrip, mean blood pressure increased (P < 0.001), whereas CBV did not change [P = not significant (NS)]. In addition, during lower body negative pressure, CBV decreased (P < 0.02; and P < 0.01, for -10 and -30 mmHg, respectively), whereas blood pressure did not change (P = NS). The dissociation between the responses of CBV and blood pressure to handgrip and lower body negative pressure is consistent with coronary vasoconstriction. During hypoxia, CBV increased (P < 0.02) and decreased during hyperoxia (P < 0.01), although blood pressure did not change (P = NS), suggesting coronary vasodilation during hypoxia and vasoconstriction during hyperoxia. In contrast, concordant increases in CBV and blood pressure were noted during the cold pressor test, and hypercapnia had no effects on either parameter. Thus the physiological stress known to be associated with sympathetic activation can produce coronary vasoconstriction in humans. Contrasting responses were noted during systemic hypoxia and hyperoxia where mechanisms independent of autonomic influences appear to dominate the vascular end-organ effects.

Evaluation of flow in the left anterior descending coronary artery but not in the left internal mammary artery graft predicts significant stenosis of the arterial conduit

OBJECTIVES

The purpose of this study was to evaluate which Doppler-derived flow index best predicts new distal left anterior descending coronary artery (LAD) stenosis in patients with left internal mammary artery (LIMA) graft.

BACKGROUND

The LIMA flow measurement has been proposed to assess graft function, but it may be misleading in case of new distal LAD stenosis and/or competitive flow from native LAD. Distal LAD coronary flow reserve (CFR: hyperemic/baseline peak flow velocity ratio) may be more appropriate.

METHODS

The LIMA and distal LAD flow was measured by transthoracic Doppler echocardiography in 96 patients undergoing diagnostic/therapeutic coronary angiography, 7 +/- 4 years after cardiac bypass surgery. The LIMA flow indexes (systolic-to-diastolic peak velocity ratio [SDPVr] >1, diastolic time velocity integral fraction [DTVIf] <0.5, and CFR <2) and LAD CFR <2 were used to predict > or =70% new LAD stenosis.

RESULTS

The LAD CFR <2 predicted new LAD stenosis, found in 21 of 77 patients without competitive flow from native LAD, with significantly higher diagnostic accuracy (98%) than LIMA flow indexes (SDPVr >1 = 61%, DTVIf <0.5 = 69%, and CFR <2 = 72%). The LIMA flow indexes were abnormal in 17 of 19 patients with competitive graft flow, but only 5 had graft restriction, and none had significant LAD stenosis. In a multivariate model of new distal LAD stenosis prediction, competitive flow from native LAD reduced the predictive role of LIMA but not of LAD CFR.

CONCLUSIONS

In patients without competitive flow from native LAD, LAD CFR is more accurate for the detection of LAD stenosis than LIMA CFR. In patients with competitive graft flow, abnormal LIMA flow patterns and blunted LIMA CFR do not reflect downstream LAD flow as LAD CFR does.

Coronary flow reserve of the angiographically normal left anterior descending coronary artery in patients with remote coronary artery disease

Coronary artery disease (CAD) has been suggested to alter coronary flow reserve (CFR; the ratio between hyperemic and baseline coronary flow velocities) not only in territories supplied by stenotic arteries but also in angiographically normal, remote regions. However, few data exist regarding the left anterior descending (LAD) coronary artery as the normal index artery. The influence of remote CAD on CFR of the angiographically normal LAD was evaluated with transthoracic Doppler ultrasound to measure CFR in the LAD during 90 seconds of venous adenosine infusion (140 microg/kg/min) in 122 subjects who were assigned to 1 group; group 1 comprised 49 controls without angiographically detectable CAD, and group 2 consisted of 73 patients with an angiographically normal LAD and remote CAD. Group 2 was divided into 4 subgroups: 16 patients with previous remote percutaneous coronary intervention (group 2A); 13 patients with significant remote stenosis (group 2B); 23 patients with previous remote myocardial infarction and percutaneous coronary intervention (group 2C); and 21 patients with previous remote myocardial infarction but no percutaneous coronary intervention (group 2D). CFR in the LAD was not significantly different in groups 1 and 2 (3.08 +/- 0.61 and 3.03 +/- 0.69, respectively, p = NS). Decreased ejection fraction and increased wall motion score index in patients with remote CAD (p < 0.00001) and multivessel CAD did not affect CFR in the LAD (group 2A 3.18 +/- 0.77; group 2B 3.05 +/- 0.65; group 2C 3.07 +/- 0.79; group 2D 2.86 +/- 0.50, respectively; F = 0.63, p = NS). In conclusion, CFR of an angiographically normal LAD is preserved in patients with remote CAD, even in the presence of previous remote myocardial infarction and wall motion abnormalities.

Usefulness of coronary flow reserve measured by transthoracic coronary Doppler ultrasound to detect severe left anterior descending coronary artery stenosis

Transthoracic coronary Doppler ultrasound during venous adenosine infusion showed damped (<1) coronary flow velocity reserve in patients with severe left anterior descending coronary artery stenosis. Damped coronary flow reserve discriminated severe from nonsevere stenosis with high sensitivity, specificity, and positive predictive accuracy, and is a unique noninvasive tool to identify high-risk patients.

Value of echocardiography in predicting future cardiac events after acute myocardial infarction

Short- and long-term survival after acute myocardial infarction mainly depends on three factors: the amount of myocardium that had become necrotic, the area of myocardium at further risk of becoming necrotic, and the patency of the infarct-related artery. Echocardiography is a low-cost, safe, bedside, repeatable tool, particularly useful for prognostic stratification after myocardial injury. Two-dimensional echocardiography analyzes left ventricular function, the most powerful predictor of survival immediately after acute myocardial infarction. Myocardial contrast echocardiography measures the infarct size and detects viable myocardium. Stress echocardiography stratifies patients with viable myocardium and/or multivessel coronary artery disease who need further diagnostic and therapeutic interventions. Transthoracic coronary Doppler ultrasonography assesses effective recanalization and coronary flow reserve of the left anterior descending coronary artery. Further technologic advances are needed to allow direct noninvasive measurement of flow by transthoracic Doppler ultrasonography in other coronary arteries.

Noninvasive coronary flow reserve assessed by transthoracic coronary Doppler ultrasound in patients with left anterior descending coronary artery stents

Noninvasive measurement of coronary flow reserve (CFR) (hyperemic/flow velocity ratio at rest) by transthoracic Doppler echocardiography showed normalization of flow in the left anterior descending (LAD) coronary artery early after stenting. We hypothesized that noninvasive CFR may reveal in-stent restenosis at follow-up. Therefore, we studied 134 patients, 0 to 72 months after successful proximal-middle LAD stenting, and 38 controls. LAD flow velocity was measured by transthoracic Doppler echocardiography during 90 seconds venous adenosine infusion (140 microg/kg/min). CFR was measured in diastole. According to angiography, patients who received stents were divided into 3 groups: group I, <50% LAD in-stent restenosis (n = 83); group II, nonsignificant (50% to 69%) LAD in-stent restenosis (n = 17); and group III, significant (> or = 70%) LAD in-stent restenosis (n = 34). LAD CFR was similar in group I and controls (2.90 +/- 0.58 vs 3.05 +/- 0.81; p = NS), it was slightly lower in group II (2.42 +/- 0.33) compared with controls and group I (p <0.001 vs both), and clearly abnormal (<2) in group III (1.38 +/- 0.48) compared with controls, and groups I and II (p <0.001). A CFR <2 had 91% sensitivity, 95% specificity, and 96% positive and 97% negative predictive values to detect significant stenosis in patients with LAD stents. Our data show that noninvasive Doppler assessment of CFR allows identification of significant LAD in-stent restenosis, based on a cut-off value of <2.

Measurement of coronary flow reserve in the anterior and posterior descending coronary arteries by transthoracic Doppler ultrasound

We describe for the first time transthoracic Doppler ultrasound assessment of coronary flow reserve (CFR) in both the posterior descending (PDA) and left anterior descending (LAD) coronary arteries. CFR (hyperemic/resting diastolic flow velocity ratio) was measured by 90-second intravenous adenosine infusion (140 microg/kg/min). Baseline PDA flow was detected in 62 of 81 subjects (76%), and the CFR was measurable in 44 of them (54%) because of adenosine-induced hyperventilation. According to angiography, these 44 subjects were divided into 3 groups: group 1 (0% to 29% stenosis), group 2 (30% to 69% stenosis), and group 3 (> or =70% stenosis). PDA CFR was 2.62 +/- 0.25 in 17 patients in group 1, 2.33 +/- 0.32 in 9 patients in group 2, and 1.40 +/- 0.54 in 18 patients in group 3 (F = 41.83, p <0.0001). LAD CFR was 3.31 +/- 0.54 in 15 patients in group 1, 2.49 +/- 0.71 in 10 patients in group 2, and 1.12 +/- 0.49 in 19 patients in group 3 (F = 65.68, p <0.0001). A cut-off of <2 identified > or =70% stenosis in both of the arteries supplying the PDA and in the LAD. Noninvasive measurement of PDA CFR is feasible and may improve with technologic advancement and the use of selective adenosine receptor agonists, thus preventing hyperventilation.

Coronary recanalization in anterior myocardial infarction: the open perforator hypothesis

OBJECTIVE

Patent perforators, noninvasively imaged by transthoracic color-Doppler echocardiography, may reflect adequate reperfusion in anterior myocardial infarction (MI).

BACKGROUND

The Thrombolysis In Myocardial Infarction (TIMI) classification may not fully reflect adequate myocardial reperfusion in MI.

METHODS

We studied 61 patients with anterior MI undergoing thrombolysis (n = 28), primary stenting (n = 20), or neither one (n = 13). High-resolution color-Doppler ultrasound was used to image the left anterior descending coronary artery (LAD) and perforators in four segments of the anterior-apical wall and to build a new recanalization score (RS). The TIMI flow was assessed by angiography. Wall motion score index (WMSI), ejection fraction (EF), end-diastolic volume index, and end-systolic volume index (ESVI) were measured by echocardiography at baseline and at three-month follow-up. Linear regression equations, considering RS or TIMI flow as independent variables, were compared among these functional recovery parameters. A multivariate linear model, predicting percent changes of WMSI, EF, or ESVI, was used to investigate the contribution of several clinical covariates along with RS and TIMI flow.

RESULTS

Sensitivity, specificity, and diagnostic accuracy of color-Doppler ultrasound in detecting LAD patency were 86%, 98%, and 97%, respectively. Mean and peak flow velocities discriminated (0.004 < p < 0.008) TIMI flow but not RS. Regression equations showed that RS discriminated better than TIMI flow recovery of ventricular function (p < 0.012). The RS was the best single multivariate predictor (p < 0.0001) of percent changes in WMSI, EF, and ESVI.

CONCLUSIONS

Transthoracic color-Doppler ultrasound detects an open LAD after MI. Perforators reflect adequate myocardial reperfusion and are early noninvasive markers of myocardial viability.

Assessment of flow velocity reserve by transthoracic Doppler echocardiography and venous adenosine infusion before and after left anterior descending coronary artery stenting

OBJECTIVES

We sought to evaluate whether coronary flow velocity reserve (CFR) (the ratio between hyperemic and baseline peak flow velocity), as measured by transthoracic Doppler echocardiography during adenosine infusion, allows detection of flow changes in the left anterior descending coronary artery (LAD) before and after stenting.

BACKGROUND

The immediate post-stenting evaluation of CFR by intracoronary Doppler has shown mixed results, due to reactive hyperemia and microvascular stunning. Noninvasive coronary Doppler echocardiography may be a more reliable measure than intracoronary Doppler.

METHODS

Transthoracic Doppler echocardiography during 90-s venous adenosine infusion (140 microg/kg body weight per min) was used to measure CFR of the LAD in 45 patients before and 3.7 +/- 2 days after successful stenting, as well as in 25 subjects with an angiographically normal LAD (control group).

RESULTS

Adequate Doppler spectra were obtained in 96% of the patients. Pre-stent CFR was significantly lower in patients than in control subjects (diastolic CFR: 1.45 +/- 0.5 vs. 2.72 +/- 0.71, p < 0.01; systolic CFR: 1.61 +/- 1.02 vs. 2.41 +/- 0.68, p < 0.01) and increased toward the normal range after stenting (diastolic CFR: 2.58 +/- 0.7 vs. 2.72 +/- 0.75, p = NS; systolic CFR: 2.43 +/- 1.01 vs. 2.41 +/- 0.52, p = NS). Diastolic CFR was often damped, suggesting coronary steal in patients with > or =90% versus <90% LAD stenosis (0.86 +/- 0.23 vs. 1.69 +/- 0.43, p < 0.01). Coronary stenting normalized diastolic CFR in these two groups (2.45 +/- 0.77 and 2.64 +/- 0.69, respectively, p = NS), even though impaired diastolic CFR persisted in three of four patients with > or =90% stenosis. Stenosis of the LAD was better discriminated by diastolic (F = 49.30) than systolic (F = 12.20) CFR (both p < 0.01).

CONCLUSIONS

Coronary flow reserve, as measured by transthoracic Doppler echocardiography, is impaired in LAD disease; it may identify patients with > or =90% stenosis; and it normalizes early after stenting, even in patients with > or =90% stenosis.